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 Post subject: Help please with Maths QuestionPosted: Thu Jul 08, 2021 9:43 pm

Joined: Sun Jun 06, 2021 4:52 pm
Posts: 12
The last question from Sevenoak 2019 Maths paper Q20.

20. The White Rabbit's (12-hour) pocket watch is running very fast! And yet it
always shows the correct time on the hour, every hour, and only on the hour.
When Alice says, "It's only half past one", what time does the White Rabbit's
watch show?
[3 marks]

I am afraid I have no clue what the question is talking about....

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 Post subject: Re: Help please with Maths QuestionPosted: Thu Jul 08, 2021 9:53 pm

Joined: Fri Mar 17, 2006 6:12 pm
Posts: 1495
Location: Birmingham
As the watch records the correct time every hour on the hour, that means the watch is fast gaining 12 hours every hour.

So the watch was correct at 1:00 so at 1:30 it will be showing 1:30 + 6 hours or 7:30

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 Post subject: Re: Help please with Maths QuestionPosted: Thu Jul 08, 2021 11:18 pm

Joined: Sun Oct 04, 2020 2:15 pm
Posts: 102
Location: Trafford
8 o'clock?

The rabbits clock is moving 13 hours per every 1 hour. At 12.00 the rabbits clock shows 12.00. And after 1 real hour, the rabbits fast clock shows 1.00 so it must have gone 13 hours.

At 1.30, the rabbits clock has gone half of 13 hours (6.5 hours).

1.30+6.5 hours= 8.00

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 Post subject: Re: Help please with Maths QuestionPosted: Fri Jul 09, 2021 9:05 am

Joined: Fri Mar 17, 2006 6:12 pm
Posts: 1495
Location: Birmingham
KaB£H1s3 wrote:
8 o'clock?

The rabbits clock is moving 13 hours per every 1 hour. At 12.00 the rabbits clock shows 12.00. And after 1 real hour, the rabbits fast clock shows 1.00 so it must have gone 13 hours.

At 1.30, the rabbits clock has gone half of 13 hours (6.5 hours).

1.30+6.5 hours= 8.00

I did have to think about this for a while but you have to remember that although the clock moves 13 hours every 1 hour it only gains 12 hours (1 hour of normal movement + 12 hours gain). So at a real time of 1:30 it will have gained 6 hours.

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 Post subject: Re: Help please with Maths QuestionPosted: Fri Jul 09, 2021 9:18 am

Joined: Sun Oct 04, 2020 2:15 pm
Posts: 102
Location: Trafford
KenR wrote:
KaB£H1s3 wrote:
8 o'clock?

The rabbits clock is moving 13 hours per every 1 hour. At 12.00 the rabbits clock shows 12.00. And after 1 real hour, the rabbits fast clock shows 1.00 so it must have gone 13 hours.

At 1.30, the rabbits clock has gone half of 13 hours (6.5 hours).

1.30+6.5 hours= 8.00

I did have to think about this for a while but you have to remember that although the clock moves 13 hours every 1 hour it only gains 12 hours (1 hour of normal movement + 12 hours gain). So at a real time of 1:30 it will have gained 6 hours.

Yes, I think you're right

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 Post subject: Re: Help please with Maths QuestionPosted: Fri Jul 09, 2021 6:01 pm

Joined: Sun Jun 06, 2021 4:52 pm
Posts: 12
KaB£H1s3 wrote:
KenR wrote:
KaB£H1s3 wrote:
8 o'clock?

The rabbits clock is moving 13 hours per every 1 hour. At 12.00 the rabbits clock shows 12.00. And after 1 real hour, the rabbits fast clock shows 1.00 so it must have gone 13 hours.

At 1.30, the rabbits clock has gone half of 13 hours (6.5 hours).

1.30+6.5 hours= 8.00

I did have to think about this for a while but you have to remember that although the clock moves 13 hours every 1 hour it only gains 12 hours (1 hour of normal movement + 12 hours gain). So at a real time of 1:30 it will have gained 6 hours.

Yes, I think you're right

KenR and KaB£H1s3,

Thank you very much both of you for the very quick response and detailed explanation and discussion.

I think I finally understand the information provided in the question, which is the clock show the correct time on 12:00, 1:00, 2:00 etc... But it does NOT imply the complete hour showing by the clock is always the correc time. (which makes the clock useless unless there is another correct watch/clock is there for comparison). This is the point I got confused. It also relies on one important assumption - the clock run faster but in a way that is linear/proportional. Therefore, for each real hour, the hour hand of the clock moves forward 13/12 rounds, i.e. 13 hours clock's time. For 30 real mins, it is 6.5 hour clock's time, so 1:30 real time is showing as 7:30 (1:00 + 6:30) in the clock.

I have to say the question is not clear at all, maybe intensionally so... Hopefully in real 11+ test, no such question will be present...

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